Climate Change

What controls Earth’s temperature?

  • Amount of energy received by the sun
  • Reflection vs absorption of sun’s energy (albedo)
  • The amount of energy retained by the earth’s atmosphere.

Amount of energy recieved by the sun

  • The path of the earth around the sun and the angle of the earth vary at different time scales.
  • Has been important influence for glacial periods (every 100,000 years) over the past 500,000 years.
  • Milankovitch Cycles

Amount of energy received from the sun?

  • Sunspots – reflect magnetic activity of sun, and sun’s brightness.
  • Approximately an 11 year cycle

Amount of energy retained by the atmosphere

  • The greenhouse effect: Energy is retained.
  • Gases in the atmosphere trap heat (CO2, CH4, NOxs, CFCs)

Global energy balance

What is “global temperature”?

Global surface temperature is calculated by averaging the temperatures over sea and land

What is “global temperature”?

  • Many groups across the world have generated datasets of global temperature
  • One example, Hansen et al. 2010 from Goddard Institute for Space Studies, NASA http://pubs.giss.nasa.gov/docs/2010/2010_Hansen_etal_1.pdf
  • Compiled different datasets from weather stations all over the world.
  • Used a model to interpolate (smooth) data for land
  • Use bucket (ships) and satellite measurements calibrated with ship measurements for the ocean

What would cause global temperature to change?

How do we measure atmospheric CO2?

  • Dr. Dave Keeling started measuring the CO2 concentration in air in 1958
  • Collected air in vacuum cleared glass flasks and measured CO2 content
  • Still measured with the method today (as well as sensors)

How do current changes compare to past climate?

  • The earth is 4.54 billion years old
  • The last ice age was 110,000 to 12,000 years ago with peak glaciation 22,000 years ago
  • The world looked different!
    • Northern USA and Canada covered by ice (grey)
    • Southern US covered by taiga (coniferous forest) and grassland
    • Southern Europe was tundra

Ice cores!

Ice cores!

Ice cores!

Key questions in module

  • What is the evidence for a changing climate?
  • How do find & interpret data sources behind main climate change indicators?
  • How do we read and plot this data in a scriptable & reproducible manner?
  • How do we communicate technical analysis in notebook formats that combine code, text, and visuals?